1. Field of the Invention
This invention relates to devices for automatically cleaning toilets. More particularly, the invention relates to means for indicating the end of useful life of the active cleansing and/or disinfectant compound used in automatic toilet cleaning devices.
2. Description of the Prior Art
Automatic (self-operating) toilet cleaners adapted for placement in the tank or cistern of a toilet are well known and generally comprise a container within which is provided a disinfectant and/or detergent composition. The container empties and refills on the occasion of a flush, and during the quiescent period between two flushes a minor amount of the disinfectant and/or detergent composition is dissolved within the container to form a suitably concentrated, typically essentially saturated, solution thereof. The essentially saturated solution is released from the container on the next flush, the essentially saturated solution being substantially diluted with tank water and then delivered at a suitable and effective cleaning/disinfecting level to the bowl.
Since the cleaning devices are often not visible and the disinfectant and detergent compositions are often colorless, there is considerable difficulty in determining when the disinfectant and/or detergent composition in the cleaning device has been depleted to the point where it is no longer effective. There is an obvious need to have some means of indicating the expiration of the useful life of such automatic toilet cleaners. Several end of life indicators have been developed. Use of a water-soluble dye as an indicator, however is not an easy solution to this problem as the essentially sautrated solutions bleach the active dye chromophores. Such prior art end of life indicators may be divided into two categories.
The first category comprises those devices using dyestuffs which are kept segregated from the water in the cistern until the active bleaching components in the water have been depleted to a predetermined level. This category of devices is represented, for example, by U.S. Pat. Nos. 4,450,594 and 3,867,101. In a non-toilet environment, a similar end of life indicator is disclosed in U.S. Pat. No. 2,451,022. U.S. Pat. No. 4,450,594 discloses a tank dispenser having a chlorine based tablet resting upon an inverted cup shaped member containing a water soluble dye. When the chlorine tablet is dissolved below a predetermined weight, the inverted cup shaped member is automatically released, thus permitting water to come into contact with the dye to create the end of life indication. In U.S. Pat. No. 3,867,101 a water soluble dye tablet is placed in the bottom of a dispenser and is totally covered with a water soluble material composition of detergent and/or disinfectant. When the detergent and/or disinfectant has been depleted to a predetermined point, the water will come into contact with the dyestuff and create the end of life indication. In U.S. Pat. No. 2,451,022 a dyestuff is contained in a core enclosed within a shell. The shell coating is shellac mixed with powdered magnesium carbonate and designed to disintegrate in a predetermined length of time in an antiseptic and germicidal solution. After the predetermined length of time, the shellac coating will be worn away and the end of life indication will occur well before the antiseptic and germicidal solution is completely exhausted.
The second category of end of life indicators comprises devices using dyestuffs admixed to disinfectant and/or detergent compositions so that the dyesuff is continuously being dissolved in the surrounding solution. Examples of devices in this second category are shown in U.S. Pat. Nos. 4,435,857, 4,229,410, 4,460,490 and 3,504,384. In a non-toilet environment, another example of an end of life indicator is shown in U.S. Pat. No. 2,449,274. In all of the devices of the second category, the colored dyestuff is continuously in contact with the surrounding water and the color is either visible or suppressed (although in the '410 patent the water is only in contact with the dyestuff during actual flushing of the toilet). The end of life indication occurs when either the dye color disappears (as in U.S. Pat. Nos. 4,229,410 and 3,504,384) or when the amount of bleach in the solution has been depleted to the point where it is insufficient to bleach the dye thereby allowing the dye color to appear (as in U.S. Pat. Nos. 4,435,857 and 4,460,490). In U.S. Pat. No. 2,449,274 the end of life indication occurs when the phenol coefficient of the composition has been reduced to a predetermined value by contamination thereby enabling the dye color to become visible.
Each of the categories of end of life indicators has certain deficiencies. The first category of end of life indicators cited above is costly to manufacture because of the need to protect the dye from premature contact with water. Additionally, those end of life indicators which are similar to that shown in U.S. Pat. No. 2,451,022 which are timed irrespective of the concentration of the active ingredient in the ambient solution may provide erroneous indications of the end of life of the active component. The second category of end of life indicators are inefficient since they require excessive amounts of dyestuffs to be utilized.
Accordingly, there is needed an end of life indicator capable of being placed in a solution and remaining in the solution until the concentration of active ingredients falls to a predetermined level and only then providing an end of life indication. It is, therefore, an object of this invention to provide a means for positively sensing the decrease in the active bleach component remaining in solution in a toilet cistern and only then enabling water to come into contact with a water soluble dye. It is a further object of this invention to provide a water soluble dye encapsulated in a bleach-impervious coating. It is yet another object of this invention to provide an end of life indicator which protects a dye from being bleached by ambient solution while enabling the dye color to be released into the ambient solution at a predetermined level of alkalinity.